International deployment of accelerometers: A network for very long period seismology

Abstract

The value to seismology of a global net of seismometers has long been recognized. Indeed, the first proposal for such a net came in 1895, only 6 years after the discovery that earthquake waves could be recorded at long distances, and the first net of standardized instruments was in existence by 1898 [Dewey and Byerly, 1969; Wood, 1942; Milne, 1899]. A true network, involving not only standardized high‐quality instruments but also the exchange and ready availability of data, did not come until the establishment of the World‐Wide Standard Seismograph Network (WWSSN) in the middle 1960's [Oliver and Murphy, 1971]. The importance of this to general seismology cannot be overstated; not only has it improved the quality of traditional research areas, but the availability of the data has suggested new types of investigations. In the decade since the WWSSN was built, two small networks have been set up: the High‐Gain Long‐Period instruments (HGLP) [Savino et al., 1972] and, very recently, the Seismic Research Observatories (SRO) [Peterson and Orsini, 1976]. Both of these networks use careful shaping of the instrument response to improve the detection of surface waves from very small events, which is important in lowering the magnitude threshold for discriminating earthquakes from explosions.

Vectorial tomography--II. Application to the Indian Ocean

“…The technical characteristics have been presented for stations are given in Table 1. They have been chosen so as the IDA network by Agnew et al (1976), for the GDSN to ensure a good spatial and also azimuthal coverage of the network by Peterson & Hutt (1982) and for the Indian Ocean. Fig.…”

Research report

“…• A differential pressure gauge [Cox et al, 1984] • A seismometer: Lacoste-Romberg gravimeter [Lacoste, 1967] -One vertical channel -Long period [Agnew et al, 1976] -Sample rate = 2 samples/sec à Nyquist frequency = 1 Hz -Levelled using motorized gimbals to within 5 x 10 -5 radians of a laboratorydetermined value -The centre value of uncertainty is approximately 1 x 10 -4…”

Re-examination of fault model for the 1982 Urakawa-oki earthquake by analyses of seismic, geodetic, and Tsunami data.

“…Since we have no observation to infer the fault parameters L, W, D of the largest aftershock, we tentatively use an empirical relation among the fault parameters of shallow earthquakes (ABE, 1975;GELLER, 1976 (AGNEW et al, 1976) network and GDSN (Global Digital Seismic Network) are used in the waveform inversion for the Urakawa-Oki earthquake and its largest aftershock, respectively. The IDA and GDSN stations used in this study are shown in Fig.…”